Interesting - I hadn't come across this yet. I'll need to look into it when I get some time. More experimentation around collaborative/federated indexes, that don't devolve into spam and poor quality webpages, can only be a good thing.
I wonder how it compares to YaCy? I deployed an instance of that recently, and while it's been good for local search (I've been using it like Hister - only to index pages that I've visited and found useful), I find the remote search to be wanting. It seems to perform better when you curate the pages it indexes, so I imagine that having category-specific instances like PeARS would help in that respect. It'd be nice to have the quality of the index come from the people maintaining it and setting the standards for what is included.